The present investigation was performed to assess the influence of age on Doppler variables of left ventricular diastolic function. Six Doppler diastolic indexes were analyzed in 86 normal volunteers ranging in age from 20 to 74 years (mean 36). All 6 indexes showed a linear relationship to age. Duration of isovolumic relaxation, duration of the early diastolic flow-velocity peak and maximal late diastolic (atrial) flow-velocity increased with age (r = 0.41, r = 0.42, and r = 0.63, respectively; p less than 0.01 to p less than 0.001). Conversely, maximal early diastolic flow-velocity, the rate of decrease (descent) of flow-velocity in early diastole, and the ratio between maximal early and late diastolic flow-velocities decreased with age (r = -0.40, r = -0.42, and r = -0.66, respectively; p less than 0.001). Comparison of Doppler indexes of diastolic function among different age groups (20 to 29 years, 30 to 49 years, and 50 to 74 years) also demonstrated an influence of age on these diastolic variables. Isovolumic relaxation was significantly prolonged in older subjects compared to either the intermediate (p less than 0.05) or the younger age groups ( p less than 0.001). In addition, both the rate of decrease of flow-velocity in early diastole and the ratio between maximal early and late diastolic flow-velocities were reduced in older compared to younger subjects ( p less than 0.001). In conclusion, the isovolumic relaxation phase and the early and late filling phases of diastole, as assessed by Doppler echocardiography, appear to be importantly affected by aging. Specifically, in older subjects, the duration of isovolumic relaxation is prolonged and the rate of early diastolic filling velocity is reduced; as an apparent compensation, the relative contribution of atrial systole to overall left ventricular filling is increased. These diastolic alterations qualitatively resemble those observed in patients with cardiac diseases associated with left ventricular diastolic impairment; hence, the effects of age should be taken into consideration in formulating "normal" limits for left ventricular diastolic function.